The present invention relates to a document reader configured to feed plural document sheets placed on a document tray one by one and read image information from each of the document sheets.
In recent years, development has been made of a document reader of the type called “single path feeder (SPF)” configured to feed document sheets one by one from a document tray to an image read position through a single document feed path and read image information from each of the document sheets.
Among such SPFs there has been proposed a SPF including two image reading devices and configured to read image information from both sides of a document sheet during one feed of the document sheet through the document feed path, as disclosed in Japanese Patent Laid-Open Publication No. 2002-182437 for example. One example of such a SPF includes both a charge coupled device (CCD) and a contact image sensor (CIS) as image reading devices.
This configuration can increase the double-side reading speed without significantly upsizing the document reader. However, there arise problems that: (1) the use of the two image reading devices having different resolving powers for reading results in a difference in image quality between two image information items read from respective of the both sides of a document sheet; (2) since the focal depth of the CCD is 3 to 5 mm whereas that of the CIS is 0.5 to 1 mm, such a difference in focal depth between the two image reading devices requires that the precision in positioning each document sheet under feeding at the image read position be strictly kept constant and is likely to cause a focusing error between the image information items read; and (3) if the image read positions of respective of the two image reading devices are situated close to each other in order to reduce the size of the device, exposure light at the image read position of one of the image reading devices is received as stray light by the other at its image read position, which results in an unsatisfactory precision in image information reading.
Though the third one of the above-described problems can be avoided by the provision of a stray light preventive member, the first and second problems cannot be solved because they are caused due to the essential difference between the CCD and the CIS.
In attempt to solve these problems, one conventional SPF includes two image reading devices each comprising a CCD. In this SPF, one of the two CCDs is disposed close to the document feed path as a part of a condensing optical system. For this reason, the document feed path is made relatively long. Accordingly, in cases where jamming of document sheets occurs on the document feed path, the jam releasing operation is required to be achieved easily. In view of this requirement, this SPF is configured to be capable of exposing the document feed path to outside.
In order to enable the SPF to expose a region of the document feed path including the image read position of the CCD forming the condensing optical system to outside, a region of an exterior panel of the device including a portion opposed to the image read position need be made openable/closable. In this case it is required that sufficient consideration be given to the shielding of the image read position from extraneous light (stray light) and the keeping of a constant precision in positioning a document sheet.
That is, it is required that: the SPF prevent extraneous light from reaching the image read position when the open/close portion of the exterior panel is closed; and the distance between a member supporting a document sheet at the image read position and the CCD agree to the designed value.
A feature of the present invention is to provide a document reader including an exterior panel having an open/close portion facing a region of the document feed path including an image read position, the open/close portion having a double structure comprising two members configured to open and close about respective fulcrums, thereby realizing the shielding of the image read position from extraneous light and the keeping of a constant precision in positioning a document sheet.